My apologies ahead of time for not having a pic....but this question is in regards to the OLDS 307 engine for my 86' FWB.

I'm trying to figure out what a particular sensor is, it's located right next to the coolant temperature sensor?........externally speaking, it looks almost identical to the coolant temperature sensor.

I know it's not the oil pressure sensor, because that's right below it.

This unknown sensor is sitting right on top of the intake manifold on the front of the engine, directly next to the coolant temp sensor.

You have two coolant temp sensors on the 307. One for the ECM/check engine light, the other for climate control operation.

sven914

08-03-11, 10:56 AM

^Almost...

The one with the yellow wire goes to the ECM as an input to vary the fuel ratio and spark timing. The ECM may use it as a parameter in engaging and disengaging the A/C Compressor, but there is nothing in my book that says that. The sensor sends a varying resistance value, which the computer can translate into an exact temperature.

The one with the green wire goes to the "COOLANT TEMP" warning lamp, mounted in the telltale. The sensor is basically an on/off switch that grounds the bulb at 260º.

tbcaddy18

08-03-11, 08:33 PM

Thanks for the responses. It's odd how they rarely, if even, mention that in the factory service manual.